The invention relates to an internal combustion engine including a motor brake arrangement, with an exhaust gas turbocharger having an exhaust gas turbine arranged in the exhaust gas line of the engine and a compressor arranged in the fresh air supply line for the engine and, furthermore, downstream of the exhaust gas turbine, a power turbine which is coupled to the engine for transferring power to the engine.
EP 0 477 579 B1 discloses an internal combustion engine with a motor brake arrangement in the form of a compression brake. The internal combustion engine includes an exhaust gas turbocharger whose exhaust gas turbine is arranged in an exhaust gas duct and whose compressor is arranged in an air intake duct of the internal combustion engine. Downstream of the exhaust gas turbine, a power turbine is arranged in the exhaust duct which is driven by the exhaust gas and coupled to the engine by a transmission. The turbine housing of the exhaust gas turbine includes a turbine wheel and downstream of the turbine wheel an exhaust gas channel is provided to which the axial power turbine is connected. The exhaust gas channel includes a by-pass arrangement with an axially movable annular slide valve whereby the exhaust gas can be conducted around the power turbine.
The exhaust gas turbine drives the compressor by way of a common shaft. The compressor sucks in air, compresses the air and discharges the compressed air to the intake duct of the internal combustion engine. The exhaust gas of the turbine is first directed to the exhaust gas turbine of the exhaust gas turbocharger and then to the power turbine which transmits the energy remaining in the exhaust gas by way of the transmission to the engine. During motor brake operation, the fuel injection is de-activated and the compression brake is activated. The compression brake opens at the end of a compression stroke the exhaust valves of each cylinder for a short period. The air compressed in the combustion chamber then escapes into the exhaust gas duct. The internal combustion engine only compresses the air and therefore provides braking power. The braking power generated by the compression of the air depends on the air flow volume passing through the engine. The air flow volume can be increased by an increased pressure difference in the exhaust gas turbine. The pressure difference can be increased for example by decreasing the exhaust gas back pressure of the exhaust gas turbine. The downstream power turbine is actually a throttling device, which increases the exhaust gas back-pressure. In addition, the power turbine driven by the exhaust gas supplies power to the internal combustion engine. In order to lower the exhaust gas back pressure and to circumvent the power turbine the bypass arrangement is opened whereby the exhaust gas is conducted through the bypass line past the power turbine.
It is the object of the present invention to provide an internal combustion engine of the type described in the introductory part of the application, but wherein the air flow volume during braking operation is increased such that the braking power of the engine is substantially increased while the power turbine is by-passed.